Method for the manufacture from sheet metal of hollow objects having a wall thickness in the closed end exceeding the wall thickness of the starting material



, 3,058,195 OF HOLLOW OBJECTS END E NG MATER XCEEDING THE IAL Oct. 16,1962 K. F. ERICSSON METHOD FOR THE MANUFACTURE FROM SHEET METAL HAVING AA L THICKNESS IN THE CLO L TH NESS OF THE STA iled Nov. 16, 1959Ill/fill!!! ICA/EL fQJLAQF EKUCSSCVV United States Patent METI-IOD FORTHE MANUFACTURE FRUM SHEE METAL 0F HGLLOW OBJECTS HAVING A WALLTHICKNESS IV THE CLOSED END EXCEEDDJG THE WALL THICKNESS OF THE STARTINGMA- TERIAL Karl Folke Ericsson, Vast-eras, Sweden, assignor toAktiebolaget Svenska Metailverken, Vasteras, Sweden, a joint-stockcompany limited of Sweden Filed Nov. 16, 1959, Ser. No. 853,383 Claimspriority, application Sweden Nov. 17, 1958 Claims. (Ci. 291.21)

The present invention relates to a method for the manufacture from sheetmetal of hollow objects closed in one end and having a wall thickness inthe closed end exceeding the wall thickness of the starting material byforming a disk of the material into a cup which by repeated procedure isreduced to its final diameter while simultaneously being increasing toits final length.

In the manufacture of such hollow objects it is a desire to start from asheet or plate having the smallest possible wall thickness, since suchplates. are economically more convenient than thicker plates and themechanical stress upon the working tools on the other hand will be lessthe more flexible, thinner and more ductile is the starting material.

One of the most important fields of application of the present inventionis the manufacture of projectile shells of the kind which is adapted tobe filled with lead for obtaining correct ballistic values. Hithertosuch projectile shells were manufactured substantimly with anessentially equal wall thickness along the entire wall, but withincreasing characteristics of resistance of the steel plates used fordefensive purposes and particularly the plates used in steel helmets,such a projectile shell lacks sufficient structural strength. This hasper se led to a desire to render possible the manufacture of suchprojectile shells having a considerable wall thickness in the closedparabolic or ogival end portions of said projectile shells. For thesolution of this problem it was earlier suggested to produce accordingto various methods blanks with concentrated wall thickness in the top ofthe projectile shell. These earlier suggestions, however, will makeconsiderable requirements upon the construction and resistance of thetools and furthermore the production of such blanks in mass production,which is obviously required, involves so esesntial economical drawbacksthat the manufacture will entail considerable economical problems.

The invention which has for its object to remove the aboveinconveniences is substantially characterized in that the material inthe closed end of the cup is upset along a predetermined outline andthat the material at the same time is allowed to move or flow out inincreasing directions of the wall thickness.

The invention also relates to a tool for carrying the method accordingto the invention into practice, particularly for the production ofprojectile shells or the like from cup-shaped blanks and ischaracterized by a punch die having a parabolic or ogival section and ashouldered punch cooperating therewith and provided with indications forthe anchoring of the blank onto it.

The invention will now be more clearly explained with reference to anembodiment diagrammatically shown in the attached drawing and inconnection therewith further characterizing features of the inventionwill be brought out.

FIGURE 1 diagrammatically shows a drawing or pressing tool which isadapted to produce a cup-shaped blank from a sheet or disk-like startingmaterial.

FIGURE 2 shows a successive tool adapted to preform 3,058,195 PatentedGet. 16, 1962 in a successive step the cup-shaped blank according toFIGURE 1 for continued drawing.

FIGURE 3 shows a further drawing tool for continued treating of thecup-shaped blank.

FIGURE 4 diagrammatically illustrates a procedure of cutting offprojecting irregularities in the open end of the cup-shaped blankresulting from the drawing operations.

FIGURE 5 illustrates a tool for the preforming of projectile shells frompreformed cup-like blanks.

FIGURE 6 shows substantially a tool according to the invention adaptedfor use in final pressing operations on the projectile shell blankmanufactured in the tool of FIGURE 5.

In FIGURE 1 of the drawing reference numeral 1 designates a punch and 2a die, which die is provided with a preferably annular fitting recess 3for a circular plate blank designated by 4. The die presents a so-calleddraweye 5 which has two coaxial circular holes 6 and 7 of differentdiameters so that an annular shoulder 8 is formed between them. Thepreferably circular blank designated by 4 is drawn or pressed by thepunch 1 through the draw-eye 5 to form a cup-shaped starting blankdesignated by 9 and located below the draw-eye. It may be mentioned asan information that with projectile shells for hand weapon ammunitionpreferably punched disks 4- are employed, having a wall thicknessamounting to approximately 1 mm, which wall thickness will notconsiderably strain the tools which have to work with accuracy and highspeed for obtaining an economic capacity of production.

In FIGURE 2 reference numerals 1t) and 11 denote sections of a furtherpunch in a successive tool. This punch is modified in such respect incomparison with the punch 1 according to FIGURE 1 that it presents anend r 11 having a less diameter than the remainder of the punch and asuitably downwardly tapering shoulder 12 located between the dilferentsections 10 and 11 of the punch. The die designated by 13 in FIGURE 2also presents a so-called draw-eye 14 which also has two hole sections15 and 16 of different diameters. In comparison with the section 6 ofthe tool according to FIGURE 1 it is presumed that the diameter of thehole 15 in the embodiment shown is somewhat less. Likewise the diameterof the hole 16 is somewhat less than the diameter of the correspondinghole 7 of FIGURE 1. By this the blank 9 being placed in the toolaccording to FIGURE 2 will obtain a less diameter after it has beendrawn through the draweye 14 to form the preformed blank 17. As will beevident from considering this blank the shoulder 12 of the punch hascaused a reduction of the wall thickness of the open end of thecup-shaped blank so as to form a thinner shell or jacket 18 at this endat the same time as the remainder of the cup has been extended in anaxial direction. I

The cup-shaped blank 17 manufactured in the tool according to FIGURE 2is thereafter placed in the tool shown in FIGURE 3 and somewhat modifiedas compared with the tool according to FIGURE 2. The punch section 19has here obtained a somewhat less diameter than the diameter of thesection 10 of the punch according to FIGURE 2. The same is applicable tothe relation between the section 20 and the section 11. Between thesections 19 and 20 there is a suitably conical shoulder. Thecorresponding draweye 22 of the punch die 23 is also divided into twoholes 24 and 25, the diameter of the hole 24 being somewhat less thanthe diameter of the hole 15 of FIGURE 2 and the diameter of the hole 25being less than the diameter of the hole 16. This means that thecup-shaped blank 17 after being drawn through the die to form a blank 26obtains a further reduced diameter and an increased length. Furthermore,it should be noted that the thin wall has been extended to form a jacket27 of a considerable length at the same time as certain irregularitiesof the edge 28 have been caused in the open end of the cup. It may bementioned that such irregularities also may occur in earlier operationsand as far as such irregularities are troublesome in the production theyshould preferably be cut off at desired times, for instance such asdiagrammatically shown in FIGURE 4, by means of for instance lathe toolsor the like 29.

The blank 26 is subjected to complete operations by first being placedin the tool shown in FIGURE 5. This tool presents a punch section 30preferably having a less diameter than the punch section 19 of FIGURE 3.Furthermore, there is a shoulder 31 and a parabolic or ogival top 32thereon. Correspondingly the die 33 presents a parabolic or ogivaloutline of the hole 34. Cut in the bottom of the hole 34 in this die 33is a fine hole 35 serving to provide communication with the atmosphere.

The blank 26 is now pressed down to the bottom of this tool whereuponthe cup-shape is transferred into the outline of a parabolic hollowobject, the closed end of which is considerably extended forwardly. Thishollow object 36 is shown in a position just before the top of the punchhas reached the bottom of the die of the tool. Difficulties would,however, arise in connection with the withdrawal of the completed blank36 from the die 33, if not particular measures were taken in order thatthe blank after the forming procedure will again be carried with thepunch out of said die. In accordance with the invention for instance thesection 30 of the punch is provided with indications in the form ofsharp-edged holes 37 or other suitable anchoring means. By the drawingprocedure thus the material of the jacket wall of the blank 26preferably from the thin section 38 will be pressed into said anchoringmeans which in other respect may be small and inconsiderable. The resultwill be that the friction thereby obtained will be sufficient for theblank to be lifted clear of said die. Thereafter the blank may beremoved from said punch in a known Way by stripper means.

i It is to be noted that particularly the closed end of the blank 36 isconsiderably extended in this drawing operation as compared with theblank 26 of FIGURE 3. The completed blank 36 is finally brought to thetool shown in FIGURE 6 and comprising a die 39 and a punch t stroke inwhich, as will be evident from the figure, the

distance between the walls of point and the Wall of the die isconsiderably increased in order to be able to receive excess materialduring the upsetting operation which is carried out in this tool on theconsiderably extended closed end of the blank shown in FIGURE 5. Inaccordance with the invention this end will be upset to follow theoutline 42 of the die 39 and the material being there by displaced isallowed to move and be forged or headed into an end product which has anogival end thickness surrounding the point 41 of the punch substantiallyeverywhere in excess of the corresponding thickness of the initial blank36. Although the materialin the figure has been shown as completelyfilling the entire space between the point of the punch and the die, itis obviously possible that the material, for instance stops at thedotted line 43, but since it maybe frequently suitable to obtain acertain defined guiding and distribution of the material, especially inconnection with such projectile objects, it may be suitable to calculatethe material which has been transferred in earlier operations to theprojectile point so that it will suffice also for accommodating theoutline of the point of the punch. It will also be seen that part of thespace designated by 44 between the punch and the die remains unfilledand the size of this hollow may'obviously be calculated according torequirement. By the procedure according to the invention starting from aplate having a relatively small thickness a hollow object has now beenprovided which presents at its end a Wall thickness which considerablyexceeds the thickness of the starting material, while obtaining theadvantages referred to in the opening statement of the description.

During the manufacturing procedure which may be carried out using adesired number of tools the cupshaped blank during the entire drawingprocess can be manufactured with a wall thickness which is below, aboveor essentially equal to that of the starting material. According to theinvention the closed end of the cup is extended through the treatmentand the upsetting operation is carried out to such an extent that thematerial in the closed end after the upsetting operation will besufficient in order to accommodate carefully to the defined outline orto obtain at least the desired wall thickness.

Particularly in the case of manufacturing projectile shells and the likeit is frequently started from plated iron sheet, for instance copperplated iron sheet. In such connection the cup is only drawn to such anextent that the plating is not broken or so that it after the upsettingoperation will again be continuous without presenting indications forpossible onset of corrosion on the protected sheet material.

During the manufacture the hollow object may obtain a Wall thickness inits open end which is below the wall thickness of the starting material.

It should also be noted that shouldered punches are used for arrestingthe material in the closed end of the cup from being considerably urgedrearwardly towards the open end during the extending and upsettingoperations respectively of the closed end of the cup. It should also bementioned that cutting operations are preferably carried out on the thinwalled projectible jacket of the cup at such places where the drawing ofthe material has contributed to deteriorate or remove the plating whichis often the case with the outermost end.

The invention is not limited to the embodiment of it described and shownbut may be varied in different ways within the scope of the basicinventive idea. Although the invention is preferred in connection withthe production of projectile shells, it may also be applied to otherhollow objects or vessels, Where it is preferred to obtain products froma material having a relatively small thickness, the bottom thickness ofwhich is larger than that of the starting material.

Having now described the invention, what I claim as new and desire tosecure by Letters Patent, is:

1. A method of making a cup like article having a thickened closed endfrom a relatively thin disc comprising forming said disc into a cupshaped element of uniform thickness, elongating said cup like elementwhile forming a shoulder in the interior thereof, deforming said elementbetween the shoulder and the closed end into desired shape by exertingpressure on said shoulder while permitting the free movement of thematerial of said element between the shoulder and the open end, anddisplacing the inner layers of material of the element towards theclosed end of the element by exerting pressure on said shoulder toobtain a thickness at the closed end which exceeds that of the originaldisc.

2. A method of making a cup like article having a thickened closed endfrom a relatively thin disc comprising forming said disc into a cupshaped element of uniform thickness, elongating said cup shaped elementwhile forming the same into two portions each having a respectiveuniform thickness and joined by a shoulder, the portion between theshoulder and the open end being of less thickness than the otherportion, deforming said element by engaging a punch on the shoulder ofthe element and forcing said punch and element into a die while freely.permitting the material of the element to move away from the closed endof the element through an annular space between the punch and the die,and displacing inner layers of material of the element towards saidclosed end by engaging a further punch on said shoulder and moving saidfurther punch towards said closed end of the element until the thicknessof the closed end exceeds a predetermined value which is greater thanthe thickness of the disc.

3. A method of making a cup like article having a thickened closed endfrom a relatively thin disc comprising forming said disc into a cupshaped element of uniform thickness, elongating said element andreducing its external diameter while forming a jacket portion of reducedthickness at the open end of the element, forming said element intoogive shape by deforming said element below the jacket portion Whilepermitting free movement of the jacket portion away from the closed endof the element, and displacing the inner layers of material of theelement towards the closed end while maintaining the ogive shape of theelement to form a closed end of increased thickness relative to that ofthe original disc.

4. A method of making a cup like article having a thickened closed endfrom a relatively thin disc comprising forming said disc into a cupshaped element of uniform thickness, the element defining a cavity,positioning a punch with a shoulder thereon into the cavity of theelement, passing said punch and element through a die to form a shoulderin said element corresponding to that of the punch, passing said elementthrough a further die by engaging the shoulder of a further punch withthat of the element to elongate said element While forming a jacketportion of reduced thickness between the shoulder and the open end,upsetting said element to desired external shape by engaging theshoulder of another punch with that of the element and deforming theelement in a further die while permitting free movement of the jacketportion away from the closed end of the element through an annular spacebetween the other punch and said further die, and displacing the innerlayers of material of the element towards the closed end thereof byexerting downward pressure on the shoulder of the element whilemaintaining the element in said further die.

5. A method as claimed in claim 2 comprising trimming the edge of saidelement at said open end before said deforming step.

References Cited in the file of this patent UNITED STATES PATENTS407,536 Kynoch et a1 July 23, 1889 726,800 Langbein Apr. 28, 19031,054,669 Bowen Mar. 4, 1913 1,323,532 Hoar Dec. 2, 1919 2,150,708Andrews et al Mar. 14, 1939 2,301,565 Moore Nov. 10, 1942 2,350,491Butler et a1. June 6, 1944 2,350,535 Sarulla June 6, 1944 2,979,188Dufiield Apr. 11, 1961

